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For the function f(x) = -2x2 + 8, what is the name of its graph, its intercepts, axis of symmetry, and how to draw it?

Mathematics

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Graph of f(x) = −2x² + 8

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Key points of f(x) = −2x² + 8
Pointxy
x-intercept−20
Maximum08
x-intercept20

Step-by-step solution

7 steps

Here are the solutions to the questions:

QUESTION 1

1.1.1. What is the name of the graph given above?

  1. Identify the form of the function.

    The function f(x)=−2x2+8f(x) = -2x^2 + 8 is a quadratic function of the form ax2+bx+cax^2 + bx + c.
    The graph of a quadratic function is a parabola.
    The name of the graph is a parabola.

    1.1.2. Calculate both the x-intercepts and y-intercepts of the graph above.

  2. Calculate the x-intercepts by setting f(x)=0f(x) = 0.

    −2x2+8=0-2x^2 + 8 = 0 8=2x28 = 2x^2 4=x24 = x^2 x=±4x = \pm\sqrt{4} x=±2x = \pm 2

    The x-intercepts are (−2,0) and (2,0)\boxed{(-2, 0) \text{ and } (2, 0)}.

  3. Calculate the y-intercept by setting x=0x = 0.

    f(0)=−2(0)2+8f(0) = -2(0)^2 + 8 f(0)=8f(0) = 8

    The y-intercept is (0,8)\boxed{(0, 8)}.

    1.1.3. What is the axis of symmetry of the graph.

  4. For a quadratic function f(x)=ax2+bx+cf(x) = ax^2 + bx + c, the axis of symmetry is given by the formula x=−b2ax = -\frac{b}{2a}.

    For f(x)=−2x2+8f(x) = -2x^2 + 8, we have a=−2a = -2 and b=0b = 0.

    x=−02(−2)x = -\frac{0}{2(-2)} x=0x = 0

    The axis of symmetry is x=0\boxed{x = 0}.

    1.1.4. Draw the graph of f(x)f(x) and show the x-intercepts and the y-intercepts on it.
    To draw the graph:

    • Plot the x-intercepts at (−2,0)(-2, 0) and (2,0)(2, 0).
    • Plot the y-intercept at (0,8)(0, 8). This is also the vertex of the parabola since the axis of symmetry is x=0x=0.
    • Since the coefficient of x2x^2 is negative (−2-2), the parabola opens downwards.
    • Draw a smooth curve connecting these points, opening downwards and symmetric about the y-axis (x=0x=0).

    1.2. The following diagram represents the graph of f(x)=ax+qf(x) = \frac{a}{x} + q. A(4;2) is a point on the graph.
    The question asks to determine the values of aa and qq.

  5. Identify the horizontal asymptote from the graph to find qq.

    From the graph, the horizontal asymptote is the line that the graph approaches as xx tends to positive or negative infinity. This line is y=1y=1.
    For a function of the form f(x)=ax+qf(x) = \frac{a}{x} + q, the horizontal asymptote is y=qy=q.
    Therefore, q=1q = 1

  6. Use the given point A(4, 2) and the value of qq to find aa.

    Substitute x=4x=4, f(x)=2f(x)=2, and q=1q=1 into the equation f(x)=ax+qf(x) = \frac{a}{x} + q.

    2=a4+12 = \frac{a}{4} + 1
  7. Solve for aa.

    2−1=a42 - 1 = \frac{a}{4} 1=a41 = \frac{a}{4} a=1×4a = 1 \times 4 a=4a = 4

    The values are a=4 and q=1\boxed{a = 4 \text{ and } q = 1}.

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